Long tolerated by the authorities, right-wing groups are now being seen as a serious threat to national security. Shaun Walker reports from Moscow

There have been a number of threats to Russia's security in recent years, from Chechen terrorism to the country's worrying demographic decline. But according to sources close to the Russian security services, what the authorities fear most in these times of economic crisis is the very thing that many Russians see as the country's saviour â€“ nationalism.

Amid a dizzying array of May Day marches, featuring various groups from across the political spectrum, all eyes were on the nationalists. They gathered around a metro station in north Moscow, as well as in other cities across the country, calling for all immigrants to be deported and a "Russia for the Russians". In the event, the Moscow meeting passed off peacefully; police arrested a few demonstrators for the possession of knives, and the rest dispersed without incident. But with a huge migrant population, poverty and unemployment among locals, and with the high oil prices that fuelled the economic boom of the past few years a fast-receding memory, many feel the time for Russia's nationalists to take the political initiative is coming soon.

Then there's Alexander Belov, Moscow's answer to the BNP's Nick Griffin. Dressed in a sharp black suit, the light of a Bluetooth receptor constantly winking over his left ear, he fingers a set of Orthodox Christian prayer beads and sips a freshly squeezed orange juice, looking like one of the thousands of well-to-do businessmen who have made decent money as Russia boomed over the past decade. But as well as being successful in the construction industry, Mr Belov is also Russia's most famous racist. He believes that the time for the nationalists to take the limelight is coming soon.

"What I want is very simple," he says, in a quiet and measured voice. "I don't want parts of Moscow to be ghettos. This city is already full of places where Russians aren't welcome, and it's unacceptable. This is a Russian city and should remain that way."

An erudite and self-assured man who heads a group of skinheads with a reputation for violence, he leads the Movement Against Illegal Immigration â€“ the DPNI, as it's known by its Russian initials â€“ one of Russia's largest far-right groups. One of its main policies is that Russia should introduce a visa regime for migrants from the former Soviet republics, sending most of the millions of Gastarbeiters (Russians use the German term to refer to guest-workers) back home.

Talking to Mr Belov and his DPNI associates is alarming. One minute they are complaining that the Russian government is corrupt, and that under Vladimir Putin civil society has been muffled and the people should be given more chance to express their democratic will (words that could come straight from the mouths of liberal opposition politicians such as the former chess grandmaster Garry Kasparov). The next minute, they are suddenly talking about cleansing Moscow of anyone who doesn't have white skin, and ranking races according to their "cultural level".

"Migrants should only be allowed if they are in the interests of society; if they have a particular skill that no locals possess, which is very unusual," says Viktor Yakushev, a giant man with a shaven head, who claims to have two higher degrees and is the DPNI's chief ideologue. "There's no denying the fact that different races have different cultural levels. You just have to look at how many black people are in prison in America, and that's after all these years of positive discrimination. Here, take Azerbaijan, for example, from where we have a lot of migrants. The society is feudal. They are unsophisticated people; they don't understand European civilisation."

The rhetoric is unpleasant, but it finds resonance among great swathes of Russian society, which is notoriously racist towards anyone with non-Slavic features. These xenophobic leanings can manifest themselves in an ugly and tasteless way, such as the tanning salons that employ African students to stand outside wearing grass skirts and holding signs that read: "I got my tan here." There is also a more sinister side to Russian racism, as evidenced by the multitude of attacks on immigrants in Moscow and across Russia.

According to Alexander Brod, the director of the Moscow Bureau of Human Rights and one of Russia's leading anti-racism campaigners, racist attacks have risen fourfold in the past five years, and may increase more sharply as the economic crisis deepens. His organisation monitors hate crimes in the country, keeping a log on its website that makes for scary reading. For one randomly selected week in April, the data shows that a Tajik citizen was murdered, citizens of Azerbaijan and Kyrgyzstan were attacked, graves were vandalised at a Jewish cemetery, and a swastika was found freshly painted on to the wall of an apartment block.

In 2008, there were 293 racist attacks, according to official statistics, including 122 deaths, but as Mr Brod points out, those that make it to the record are just the tip of the iceberg. Given that many migrant workers are in Russia illegally, they are afraid to report attacks, and indeed many see the police as more of a threat than the skinheads. Nobody knows how many attacks there really are, but most immigrants have stories of being threatened, at the very least, during their time in Russia.

Russia has more than 10 million immigrants by some estimates, giving it the second-largest immigrant population in the world, after the United States. Most of them are from the impoverished former Soviet republics of central Asia and the Caucasus, who come to Russia to earn cash to send to their families back home. Now, with the financial crisis bringing Russia's economic boom to a grinding halt, hundreds of thousands of migrant labourers who were the engine behind the construction frenzy that overtook Moscow and other Russian cities find themselves out of work. At the same time, unemployment and anger are on the rise among ethnic Russians. Analysts say it could be a dangerous combination, and people such as Mr Belov believe their moment is nigh.

He has come to the interview straight from a hearing in a court case, where he stands accused of inciting racial hatred and faces up to a year and a half in prison if convicted. It seems to be one of many signs that the Russian authorities, who for a long time have at the very least turned a blind eye to nationalist movements, are beginning to get worried. Whereas the DPNI and groups such as the Slavic Union used to have powerful backers among members of Russia's Duma, and according to rumours, even within the presidential administration, it now seems that the word has gone out that the nationalists should be muffled. While nationalist posturing towards the West and Nato is a mainstay of Russian foreign policy, there is now a growing realisation that nationalism within the country could be a dangerous force if it gets out of control.

"There is mass unemployment in the country, and the economic crisis is getting worse," Mr Belov says. "The authorities are scared of people who find a common language with the masses and tell the truth." He claims that he preaches an ideology of non-violence: "By trying to sideline me, they will only promote a real wave of violence," he says.

"I've heard from sources in the Moscow FSB [Federal Security Service] that they have been told that in this time of economic crisis, nationalism is a bigger threat to national security than terrorism," says Andrei Soldatov, one of the leading experts on the Russian security services.

A recent mockumentary film called Russia 88, which so far has failed to find a cinema chain in Russia willing to show it, highlights the issue. Shot using grainy footage from handheld cameras, the film follows a group of Russian skinheads as they beat up immigrants in the metro and on the street. The skinheads are played by actors, says the director, Pavel Bardin, but all the neo-Nazi clothing and paraphernalia was bought from real Russian online shops, many of the words are taken from internet forums, and the on-street vox pop, where many people are seen voicing racist statements and declaring that "Russia is for the Russians", is real.

While genuine neo-Nazis will remain on the periphery and never gain widespread popularity in a country that still feels immense pride in its role in the defeat of fascism during the Second World War, the casual racism and hatred of immigrants that could provoke a nationalist uprising are certainly there in abundance. Indeed, some surveys show that up to 60 per cent of Russians agree with the slogan "Russia for the Russians", the catchphrase of Russian nationalists.

"There is no legal way for people to express their dislike for immigrants," Mr Yakushev says. "This means there will be increasing street violence. There will be killings and bombs."

The latest attempts by the authorities to silence people like Mr Belov are overdue, but are unlikely to be effective, rights campaigners say.

"Racism is like a dragon, where you cut off one head and another simply grows back in its place," Mr Brod says. "The authorities are trying to fight xenophobia with punitive measures, but the only way to do it properly is to combine this with solutions to the root causes of nationalism â€“ poverty, unemployment, and young people who have no prospects."

"The object of life is not to be on the side of the majority but to escape finding oneself in the ranks of the insane." Marcus Aurelius, Roman Emperor and stoic philosopher, 121-180 A.D.

"It takes far less effort to find and move to the society that has what you want than it does to try to reconstruct an existing society to match your standards." - Harry Browne, How I Found Freedom in an Unfree World